This application describes and claims certain improvements in the electrochemical cell disclosed in U.S. Pat. No. 3,791,871.
The basic mechanism of operation of the cell described in the aforementioned patent is incorporated by reference in this application. Briefly, the cell utilizes a reactive metal anode highly reactive with a aqueous electrolyte and spaced from the cathode by an electrically insulating film which forms naturally on the anode in the presence of water. This thin film permits the cathode to be placed in direct contact with the anode. The resulting reduction in the anode-cathode spacing to a thickness no greater than the thickness of this thin film greatly reduces the I.sup.2 R losses which would otherwise be present and results in increased power output and energy density. The anode and cathode operate in an aqueous electrolyte which supports the beneficial electrochemical reaction.
The aqueous electrolyte, however, also supports a parasitic chemical reaction with the non-working surfaces of the anode which reduces anode size and hence energy efficiency of the cell. Such parasitic loss results in no useful electrochemical reaction and is particularly serious where the area of the non-working anode surface is large in comparison to the area of the working surface.